Method of hot stamping metal parts

ABSTRACT

A method of producing a stamped composite part, the method comprising spot welding two or more metal component parts to each other to hold the component parts in a selected position as a composite part, heating the composite part, and stamping the composite part into a desired shape. The invention also contemplates the further step of welding the two or more metal component parts to each other in the composite part.

FIELD OF THE INVENTION

This invention relates to the process and systems of hot stamping metalparts. In particular, this invention relates to a process of hotstamping and joining metal parts.

BACKGROUND OF THE INVENTION

Metal parts are often formed from sheet metal. Sheet metal is cut, bentand pressed in to the shape of the desired metal parts. After the metalpart is formed, it can then be welded or otherwise attached to othermetal parts created by the same process or by other means.

Hot stamping is a process of forming metal parts from sheet metal stockthat involves heating a portion of the sheet metal material to a hightemperature for a period of time and then forming the heated materialusing a die.

Ovens are often used to heat the pieces to the high temperatures needed.In a manufacturing facility, pieces may be continuously moved throughthe oven so the parts are consistently heated to the desired temperaturefor the desired length of time. Ovens are generally an expensive elementof the manufacturing facility, in terms of both capital and operatingcosts, and the throughput of the oven a limiting factor in the hotstamping process.

The part may then be stamped to form the metal part into the desiredshape. Stamping is the forming of metal by using a die and a punch thatresembles the shape of the part. By heating the piece, the metal becomesmore ductile and easier to form by pressing within the die.

After being pressed in the die, the formed piece may be quenched byrapidly cooling the part, often using water. Quenching of the metalgenerally improves certain properties in the metal such as hardness andstrength that would not otherwise be present if cooled gradually.

After the part is cooled, it may be welded or otherwise attached toother parts to create a composite metal component. As often multipledifferent parts must be welded together, multiple dies must be used toform each of the parts before they can be welded together, and each ofthe parts must be separately heated in the oven before stamping.

Hot stamping facilities may hot stamp a first part for a period of timeby cutting, heating and stamping the first part. After a suitablequantity of the first part has been created, a second part may be hotstamped by cutting, heating and stamping the second part. Only after thesecond part is formed, may the first and second parts be weldedtogether. This process requires that a suitable quantity of the firstpart be stored pending the hot stamping of the second part.Alternatively, a manufacturer must run multiple ovens at the same timein order to heat the first and second parts in parallel, with attendantadditional cost and space usage.

Moreover, it is conventionally considered that the integrity of a weldbetween parts that are welded together before the parts are heated to asufficiently hot temperature for hot stamping is suspect, in contrast towelds effected after the hot stamping process.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate by way of example only a preferredembodiment of the invention,

FIG. 1 is a flow chart showing the hot stamping process according to animplementation of the invention.

FIG. 2 is a plan view of a composite blank before being hot stamped.

FIG. 3 a perspective view of a component part after being hot stamped.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method of producing a stampedcomposite part, the method comprising the steps of cutting at least twometal component parts into a desired shape; welding the at least twometal component parts to each other to hold the at least two metalcomponent parts together in a selected position as a composite blank;heating the composite blank for stamping; and stamping the compositeblank to form the composite blank into a desired shape, thereby creatinga stamped composite part.

The method may further comprise the step of further welding the at leasttwo metal component parts to each other in the composite part.

With reference to FIG. 1, the process is described in relation tocreating a stamped component made from two metal component parts. Theprocess of the invention can be used to create a stamped composite partmade from more than two metal component parts. As used herein, a metalcomponent part is a single part of metal formed from a single part ofsheet metal stock, for example cut as a “blank,” that may then be formedand/or welded to another part. Other forms of source material may beused in place of sheet metal stock, such as bar, tube or wire. Acomposite part consists of two or more metal component parts that havebeen formed and welded together.

In the two-component embodiment of the invention described andillustrated by way of example only, as shown at 1 and 2 each of the twometal component parts is cut from sheet metal stock. The sheet metalstock may be cut to form the metal parts using any suitable technique,for example without limitation, punching, laser cutting, trimming, orshearing, to create blanks.

At block 5, the two component parts are arranged together in a selectedposition and held in the selected position with one or more welds, forexample spot welds as indicated. The spot welds retain the two parts inthe selected position during the heating step 10 and the stamping step20. The retaining spot welds may be effected manually or by a machinedesigned to position and spot weld the parts. In one preferredembodiment the component parts 100, 105 are further welded togetherafter stamping to augment the strength of the composite part 115.

As shown in FIG. 2, an example of a first component part 100 and asecond component part 105 are held in alignment using five aligning spotwelds indicated as 110. This creates a composite part 115, at this stagestill an unformed blank.

At block 10, the two component parts are heated, by a heating apparatus,for example a furnace or oven. As mentioned, the two component parts areheld together by the retaining spot welds completed at block 5, creatinga composite blank 112. The two parts 100, 105 are heated in the heatingapparatus preferably to a sufficiently high temperature to prepare thecomposite blank 112 for the stamping step 20, for example by renderingthe composite blank 112 ductile. After heating the composite blank 112,the composite blank 112 is removed from the heating apparatus asindicated at block 15. The heating apparatus may be a walk through ovensuch as used in conventional hot stamping processes. Alternatively, theheating apparatus may be an oven with one or more compartments suitablefor placing a part. The composite blank may be heated to 920 degreesCentigrade for between 4 to 10 minutes. Heating the composite blank 112for an undue lengthy period of time may cause damage to any coating onthe surface of the two parts 100, 105.

At block 20, the heated composite blank 112 is placed in a die andpressed using a hot stamping press. The die forms both of the componentparts 100, 105 while the component parts are sufficiently ductile fromthe heating process 10, the retaining spot welds from step 5 beingsufficient to maintain the two component parts 100, 105 in positionrelative to one another during the stamping stage 20.

At block 25, the heated and formed composite part 115 is quenched byrapid cooling, as is conventional. Quenching may be done using water orgas or any other suitable technique. In one embodiment, the die andpunch are cooled by water flowing through ducts integrated with the dieand punch so that quenching occurs substantially simultaneously with thestamping process. After being hot stamped, the composite part 115 may beneed to be cleaned to remove scale from the heating and forming steps.

After the composite part 115 has been hot stamped, the component parts100, 105 may be further welded together to augment the strength orintegrity of the composite part 115, as indicated at block 30, morefully integrating the two component parts 100, 105 with the shape andnumber of welds desired. An example of a completed composite part 115prepared according to the invention is shown in FIG. 3.

By positioning the two component parts 100, 105 prior to heating thecomposite blank 112 in the oven, the throughput of the overall processmay be increased.

The integrity of the retaining spot welds is maintained through theheating and stamping parts of the process.

The process of hot stamping as described above may involve other stepssuch as quality assurance and dimensional checking as part of themanufacturing process.

In a composite part 115 produced according to the method of theinvention the integrity of the retaining welds between the componentparts 100, 105 is retained despite heating the component parts to asufficiently hot temperature for hot stamping.

1. A method of producing a stamped composite part, the method comprisingthe steps of: a) cutting at least two metal component parts into adesired shape; b) welding the at least two metal component parts to eachother to hold the at least two metal component parts together in aselected position as a composite blank; c) heating the composite blankfor stamping; and d) stamping the composite blank to form the compositeblank into a desired shape, thereby creating a stamped composite part.2. The method of claim 1 further comprising after step d), the step of:e) further welding the at least two metal component parts to each otherin the composite part.
 3. The method of claim 2, wherein step b)comprises the step of spot welding the at least two metal componentparts to each other using at least four spot welds.
 4. The method ofclaim 2, wherein step c) comprises the sub-steps of: i) placing thecomposite part in an oven; ii) heating the composite part in the oven;and iii) removing the composite part from the oven.